SummaryMacrophages are strongly adapted to their tissue of residence. Yet, little is known about the cell-cell interactions that imprint the tissue-specific identities of macrophages in their respective niches. Using conditional depletion of liver Kupffer cells, we traced the developmental stages of monocytes differentiating into Kupffer cells and mapped the cellular interactions imprinting the Kupffer cell identity. Kupffer cell loss induced tumor necrosis factor (TNF)- and interleukin-1 (IL-1) receptor-dependent activation of stellate cells and endothelial cells, resulting in the transient production of chemokines and adhesion molecules orchestrating monocyte engraftment. Engrafted circulating monocytes transmigrated into the perisinusoidal space and acquired the liver-associated transcription factors inhibitor of DNA 3 (ID3) and liver X receptor-α (LXR-α). Coordinated interactions with hepatocytes induced ID3 expression, whereas endothelial cells and stellate cells induced LXR-α via a synergistic NOTCH-BMP pathway. This study shows that the Kupffer cell niche is composed of stellate cells, hepatocytes, and endothelial cells that together imprint the liver-specific macrophage identity.

Resistance to Trypanosoma brucei brucei has been correlated with the ability of infected animals to produce interferon (IFN)-gamma and tumor necrosis factor (TNF) in an early phase of infection, followed by interleukin (IL)-4 and IL-10 in late and chronic stages of the disease. Contributions of IFN-gamma and IL-10 in the control of parasitemia and survival of mice infected with T. brucei brucei were investigated by using IFN-gamma(-/-) and IL-10(-/-) mice. Results suggest that IFN-gamma, mainly secreted by CD8(+) T cells, is essential for parasite control via macrophage activation, which results in TNF and nitric oxide secretions. IL-10, partially secreted by CD4(+) T cells, seems to be important for the survival of infected mice. Its absence resulted in the sustained secretion of inflammatory mediators, which indicated the role of IL-10 in maintaining the balance between pathogenic and protective immune responses during African trypanosomosis.

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Coelomic fluid of Eisenia foetida earthworms contains a 42-kDa protein named coelomic cytolytic factor 1 (CCF-1) that was described previously to be involved in cytolytic, opsonizing, and hemolytic properties of the coelomic fluid. Cloning and sequencing of CCF-1 reveal significant homology with the putative catalytic region of ␤-1,3-and ␤-1,3-1,4-glucanases. CCF-1 also displays homology with coagulation factor G from Limulus polyphemus and with Gram-negative bacteria-binding protein of Bombyx mori silkworm, two proteins involved in invertebrate defense mechanisms. We show that CCF-1 efficiently binds both ␤-1,3-glucan and lipopolysaccharide. Moreover, CCF-1 participates in the activation of prophenoloxidase cascade via recognition of yeast and Gram-negative bacteria cell wall components. These results suggest that the 42-kDa CCF-1 protein of E. foetida coelomic fluid likely plays a role in the protection of earthworms against microbes.The prophenoloxidase (pro-PO) 1 -activating system represents an important defense mechanism in a large variety of invertebrates (reviewed in Refs. 1 and 2). This system is based on the recognition of bacterial antigens such as lipopolysaccharide (LPS) or peptidoglycan and ␤-1,3-glucan present as major components of the cell wall of yeast and fungi (3,4). Generally, upon the recognition of such saccharides proteases cleave by limited proteolysis inactive pro-PO to its active state, phenoloxidase (PO). The active enzyme catalyzes the o-hydroxylation of monophenols as well as the oxidation of diphenols to quinones that are subsequently polymerized nonenzymatically to melanin. Melanin and its precursors involved in the pro-POactivating system have cytotoxic and antimicrobial properties and participate in a wide range of other biological activities including phagocytosis/opsonization, encapsulation/nodule formation, degranulation, and wound healing (5-9).The pro-PO-activating system has been detected both in protostomian and deuterostomian species. Although pro-POactivating system is well documented in arthropods, data in other protostomian groups are more scarce. In annelids, melanization reactions and formation of "brown bodies" or nodules have been described in polychaetes and oligochaetes (10 -14). However, biochemical detection of PO activity was so far restricted to a few species with rather controversial results. Whereas Smith and Söderhä ll (15) failed to detect pro-PO system in the polychaete Aphrodite aculeata and Arenicola marina, Fischer (16), Valembois et al. (17), and Porchet-Hennerè and Vernet (13) have documented PO activity in Lumbricus terrestris, Eisenia foetida andrei, and Nereis diversicolor, respectively. More recently using L-DOPA as substrate, a 38-kDa protein responsible for PO activity was identified in the coelomic fluid of E. foetida andrei (18). A report showing that the oxidative activity of the coelomic fluid of earthworms toward L-DOPA in vitro is not affected by trypsin but completely blocked by subtilisin reflects the importance of a correct proteolyt...

Processing of fibrillar collagens is required to generate collagen monomers able to self-assemble into elongated and cylindrical collagen fibrils. ADAMTS-2 belongs to the "A disintegrin and metalloproteinase with thrombospondin type 1 motifs" (ADAMTS) family. It is responsible for most of the processing of the aminopropeptide of type I procollagen in the skin, and it also cleaves type II and type III procollagens. ADAMTS are complex secreted enzymes that are implicated in various physiological and pathological processes. Despite accumulating evidence indicating that their activity is regulated by ancillary domains, additional information is required for a better understanding of the specific function of each domain. We have generated 17 different recombinant forms of bovine ADAMTS-2 and characterized their processing, activity, and cleavage specificity. The results indicated the following: (i) activation of the ADAMTS-2 zymogen involves several cleavages, by proprotein convertases and C-terminal processing, and generates at least seven distinct processed forms; (ii) the C-terminal domain negatively regulates enzyme activity, whereas two thrombospondin type 1 repeats are enhancer regulators; (iii) the 104-kDa form displays the highest aminoprocollagen peptidase activity on procollagen type I; (iv) ADAMTS-2 processes the aminopropeptide of ␣1 type V procollagen homotrimer at the end of the variable domain; and (v) the cleaved sequence (PA) is different from the previously described sites ((P/A)Q) for ADAMTS-2, redefining its cleavage specificity. This finding and the existence of multiple processed forms of ADAMTS-2 strongly suggest that ADAMTS-2 may be involved in function(s) other than processing of fibrillar procollagen types I-III.Collagens types I-III are synthesized as precursors (procollagens) formed by a central triple helical collagen domain extended by propeptides at both extremities. Removal of the C-propeptide, 3 by BMP-1 and related enzymes, and the N-propeptide, by aminoprocollagen peptidases (ADAMTS-2, -3, or -14), is required to generate collagen monomers able to assemble spontaneously into elongated and cylindrical collagen fibrils. It has been shown in vitro and in vivo that ADAMTS-2 is the enzyme responsible for most of the aminoprocollagen type I processing in the skin (1-3), although it was suggested that an essential function of ADAMTS-3 is the processing of aminoprocollagen type II in cartilage (4). A closely related enzyme, ADAMTS-14, also displays aminoprocollagen peptidase activity (5). More recently, it has been shown that ADAMTS-2 is also able to process aminoprocollagen type III in vitro (6). Type V collagen is a minor fibrillar collagen. Among the four different individual collagen type V chains, ␣1 is the most abundant and ubiquitous and can be found as a homotrimer or as a heterotrimer in association with type V or type XI ␣ chains (7,8). Its maturation from procollagen to collagen is reported to be different from what is observed for procollagens I-III, because the C-propeptide can...

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In order to evaluate during experimental Trypanosoma brucei infections the potential role of tumor necrosis factor alpha (TNF-α) in the host-parasite interrelationship, C57BL/6 TNF-α knockout mice (TNF-α−/−) as well as C57BL/6 wild-type mice were infected with pleomorphic T. bruceiAnTat 1.1 E parasites. In the TNF-α−/− mice, the peak levels of parasitemia were strongly increased compared to the peak levels recorded in wild-type mice. The increased parasite burden did not reflect differences in clearance efficacy or in production ofT. brucei-specific immunoglobulin M (IgM) and IgG antibodies. Trypanosome-mediated immunopathological features, such as lymph node-associated immunosuppression and lipopolysaccharide hypersensitivity, were found to be greatly reduced in infected TNF-α−/− mice. These results demonstrate that, during trypanosome infections, TNF-α is a key mediator involved in both parasitemia control and infection-associated pathology.

Mechanisms regulating resistance to African trypanosomes were addressed by comparing the immune responses of mice infected with attenuated Trypanosoma brucei brucei lacking the phospholipase C gene (PLC-/-) and those of mice infected with wild-type (WT) parasites. Inhibition of concanavalin A (ConA)-induced T cell proliferation occurred in spleen and lymph nodes of PLC-/-- and WT-infected mice. Although suppressive cells were elicited in spleen and lymph nodes of WT-infected animals, such cells were not detected in lymph nodes of PLC-/--infected mice. PLC-/--infected mice had more interleukin-4 and -10 in their blood than did WT-infected mice. Correspondingly, PLC-/--infected mice had higher IgG1 antibody levels against variant surface glycoprotein than did WT-infected mice. These data indicate that attenuation of T. b. brucei correlates with the absence of cells suppressing ConA-induced T cell proliferation in the lymph nodes, with increased production of Th2 cytokines and a stronger IgG1 antibody response to trypanosome antigens.